The 258mm based converter takes over where the 245mm units leave off. I generally point folks making over 850ftlbs or 3600lbs vehicle weight to the 258. There is some room for opinion here. I often put folks with big rims, off road applications or other considerations into the 258mm. These have a tendency to drive more “factory” than the smaller units.
The 258 is the core of choice for most modern converter companies at power levels over 850ft lbs of torque. There are two different factory impeller (pumps) and 3 different OEM stators, so the power range and stall speed is very adjustable even before we get to the aftermarket stators available (of which there are nearly 2 dozen)
Because the 258 is likely to see such high power, I recommend considering a swap to a mechanical diode. This replaces the factory roller clutch with a much stronger assembly. I have detailed pictures below.
As of May 2026 my 258 prices are $1050 for 4L80 single billet oem stator, $1175 for triple disc OEM stator, add $550 for mechanical diode.
Turbo 400 258mm price $975, add diode $450, sprag delete $200
Every converter is fully tig brazed thoughout, billet cover, anti-ballon plated impeller and balanced as parts, and as an assembly.
I can also converter any 258 to bolt together for $1000 additional parts and labor
I generally do not shelf stock these as application and configuration can vary so much. Please call 503 560 1852 or email me truckdoug@The4L80eGuy.com to discuss your needs.
The 258mm based converter takes over where the 245mm units leave off. I generally point folks making over 850ftlbs or 3600lbs vehicle weight to the 258. There is some room for opinion here. I often put folks with big rims, off road applications or other considerations into the 258mm. These have a tendency to drive more “factory” than the smaller units.
The 258 is the core of choice for most modern converter companies at power levels over 850ft lbs of torque. There are two different factory impeller (pumps) and 3 different OEM stators, so the power range and stall speed is very adjustable even before we get to the aftermarket stators available (of which there are nearly 2 dozen)
Because the 258 is likely to see such high power, I recommend considering a swap to a mechanical diode. This replaces the factory roller clutch with a much stronger assembly. I have detailed pictures below.
As of May 2026 my 258 prices are $1050 for 4L80 single billet oem stator, $1175 for triple disc OEM stator, add $550 for mechanical diode.
Turbo 400 258mm price $975, add diode $450, sprag delete $200
Every converter is fully tig brazed thoughout, billet cover, anti-ballon plated impeller and balanced as parts, and as an assembly.
I can also converter any 258 to bolt together for $1000 additional parts and labor
I generally do not shelf stock these as application and configuration can vary so much. Please call 503 560 1852 or email me truckdoug@The4L80eGuy.com to discuss your needs.
